The statements in this section merely provide background information related to the present disclosure and do not constitute prior art.
Moving Picture Experts Group (MPEG) and Video Coding Experts Group (VCEG) have developed an improved and excellent video compression technology over existing MPEG-4 Part 2 and H.263 standards. The new standard is named H.264/AVC (Advanced Video Coding) and was released simultaneously as MPEG-4 Part 10 AVC and ITU-T Recommendation H.264. Such H.264/AVC (hereinafter referred to as ‘H.264’) uses a spatial predictive coding method, which is different from known video coding international standards such as MPEG-1, MPEG-2, MPEG-4 Part2 Visual and the like.
Known video coding methods use “intra prediction” for coefficients transformed in Discrete Cosine Transform Domain (or DCT Transform Domain) to seek higher encoding efficiency resulting in degradation of the subjective video quality at low band transmission bit rates. However, H.264 adopts a method of encoding based on a spatial intra prediction in a spatial domain rather than in a transform domain.
Encoders using an encoding method based on the known spatial intra predictions predict a block to currently encode from information of the previously encoded and reproduced previous blocks, encode information on just the difference of the predicted block from the actual block to encode and, transmit the encoded information to a decoder. At the same time, the encoder transmits parameters needed for prediction of the block to the decoder, or the encoder and decoder are synchronized, so that they share the needed parameters for the decoder to predict the block. At the decoder, prediction of the current block is carried out by using neighboring blocks upon completion of their decoding and then the difference information transmitted from the encoder is added to the predicted current block to reconstruct the target block information to presently decode. Then, again, if the parameters needed for the prediction are transmitted from the encoder, the decoder uses the parameters in predicting the current block.
However, the inventor(s) has noted that when a prediction is performed with respect to the current block according to the typical video encoding/decoding methods, the previously encoded adjacent pixels included in the blocks neighboring (mostly at the left and upper sides of) the block to presently encode, i.e. current block. The inventor(s) has experienced that in this occasion, the current block pixels which are farther from the adjacent pixels in the neighboring blocks are predicted by using the adjacent pixels that have a greater distance and thus the accuracy of prediction is lowered. The inventor(s) has experienced that the less accurate prediction will increase the difference between the actual pixel value and the predicted pixel value, resulting in decreased compression efficiency.